Countries have pledged tens of millions for family planning schemes in developing countries to plug a gap left by Donald Trump’s ban on US funding to groups linked to abortion.

About 50 governments are attending the hastily convened She Decides conference in Brussels on Thursday, with early pledges closing in on $100m (£80m).

Sweden promised $22m and Finland $21m to compensate for the reinstated “global gag rule”, which bans US funding for NGOs that provide abortion or information on the procedure to women in developing countries.

The UK has sent the international development minister, Rory Stewart, to the one-day conference, but it remains unclear if the government will announce a financial contribution.

Organisers hope to raise $600m. “This is not a conference against the American administration; this is a conference for something,” Sweden’s deputy prime minister, Isabella Lövin, told the Guardian.

“We are expressing our strong support for women’s rights, for the progress that has been made. Access to contraceptives and sexual reproduction is a vehicle for development and the eradication of poverty.”

In an executive order signed last month, Trump reinstated the global gag rule, a US aid policy Republican presidents since Ronald Reagan in 1984 have imposed but their Democrat counterparts have lifted.

Sweden’s international development minister cited evidence from the World Health Organization showing that, under George W Bush’s presidency, the rule increased abortions and maternal deaths from unsafe terminations. “This is something we can prevent,” she said.

Alexander De Croo, Belgium’s deputy prime minister, told the Associated Press: “This should not be a moment where we are taking steps back into the dark ages.”

Belgium, Denmark, the Netherlands and Norway have pledged $10m each, with further contributions expected to be announced by other wealthy countries.

A government spokeswoman was unable to confirm whether he would announce any financial contribution from the UK.

The Department for International Development has previously described the UK as a global leader on family planning. It points to “a major international summit this summer to secure commitments that increase access to family planning services for women and girls in the world’s poorest and most fragile countries”.

Other wealthy countries are expected to announce donations. Canada’s minister of international development, Marie Claude Bibeau, said: “Women’s rights begin with their right to control their bodies. We should never take that away from them, especially for young adolescents. Canada is proud to stand with its partners and will always stand up for women’s rights everywhere.”

Afghanistan, Chad and Ethiopia are among the developing countries sending representatives to the conference, where they are expected to give evidence on how funding for family planning makes a difference to women’s lives.

Organisers have also expressed hope that US foundations may get involved by contributing funds. While the conference has been warmly welcomed by NGOs, some have voiced fears the money cannot be raised quickly enough to fill the shortfall left by Trump’s executive order.

Lövin expressed hope of hitting the target, but said Thursday’s conference was only the first step.

But she brushed aside questions she was mocking Trump and his administration, saying: “The message was not that we were only women in that picture; the message was that we are taking leadership when it comes to tackling climate change.

“This was my staff and myself and my state secretaries and I was signing a bill and that’s all.”